1. Field of the Invention
The present invention relates to a special spatial warp knitted structure produced by warp-knitting a textile, a method of manufacturing the same, and a warp knitting machine for knitting the same, more specifically to a novel spatial warp knitted structure incorporating insert threads or a simulated woven structure and knitted on a warp knitting machine having two needle bars, such as a double needle bar Raschel machine, or a special warp knitting machine developed through the modification of a double needle bar warp knitting machine, a method of manufacturing practical spatial warp knitted structures based on such a spatial warp knitted structure incorporating laid-in threads or a simulated woven structure, and a special warp knitting machine capable of knitting such a novel spatial warp knitted structure.
2. Description of the Related Art
In recent years, composite materials comprising textiles have been applied to many fields including daily commodities and utensils, not to mention aeronautics and military fields for the purpose of weight reduction, toughness enhancement, shock absorption, heat insulation, and/or sound isolation.
From the functional point of view, textiles are used often in a spatial structure, typically represented by a honeycomb structure, to meet the purposes. However, ordinary flat textile structures as woven or as knitted cannot be used to form a spatial structure. Accordingly, in constructing a honeycomb structure, for instance, by ordinary flat fabrics having the shape of a sheet, the flat fabrics are turned into corrugated fabrics by means of corrugated rollers, and then the corrugated fabrics are joined adhesively in a parallel, layered arrangement, or layers of fabrics are joined in a parallel, layered arrangement, or layers of fabrics superposed one over another are joined adhesively at bonding points distributed in a three-dimensional, zigzag pattern, and then the layers of the fabrics thus bonded are expanded in a spatial structure. However, such a method of constructing a spatial structure requires complicated processes, and the spatial structure thus formed involves a problem that the layers of fabrics are liable to separate from each other.
In view of such difficulties, a compound fabric formed by adhesively bonding flat woven fabrics superposed one over another, or a multiple layer fabric consisting of several distinct woven fabrics united by threads of warp or weft passing across the adjacent distinct woven fabrics, has been used.
U.S. Pat. No. 4,183,232 discloses a method of knitting a spatial textile structure on a circular knitting machine.
A laminated and adhesively bonded fabric structure can easily be increased in thickness; however, such a fabric structure requires much time and labor for manufacture and has insufficient shearing strength, although the tensile strength thereof is high, because such a fabric structure does not have threads extending in the direction of the thickness. A multilayer fabric consisting of several distinct woven fabrics united by threads of warp or weft passing across the adjacent distinct woven fabrics has sufficient shearing strength; however, the thickness of such a multiplier fabric is limited. U.S. Pat. No. 4,183,232 discloses a spatial knitted structure having threads respectively extending in three-dimensional directions. However the conformation of the spatial knitted structure is limited to either a cylindrical shape or a conical shape. Furthermore, since the vertical threads of this spatial knitted structure are inserted in a separate process, it is difficult to construct the spatial knitted structure in a high textile density.
Another known spatial knitted structure is knitted on a warp knitting machine, such as a double Raschel machine equipped with two needle bars. This known spatial knitted structure is formed, as illustrated in FIG. 1 by way of example, by uniting two distinct knitted fabrics 7 and 7' respectively consisting of loops 1 and 1' with uniting threads 2. This spatial knitted structure is divided into two individual pile fabrics by cutting the uniting threads, and the pile fabrics are used widely for the upholstery of automotive seats and blankets; however, the application of the spatial knitted structure as knitted to industrial materials has never been proposed. However, this known spatial knitted structure has a problem in industrial application that, although the strength along the wale and course is high enough, the compressive strength thereof is very low, and is unsatisfactory in three-dimensional appearance due to its limited thickness.